The term "filament" is used herein generically, and does not necessarily exclude cut fibers (often referred to as staple), although synthetic polymers are generally prepared initially in the form of continuous polymeric filaments as they are melt-spun (extruded). Most synthetic polymeric filaments are melt-spun, i.e., they are extruded from a heated polymeric melt. This has been done for more than 50 years, since the days of W. H. Carothers, who invented nylon. Nowadays, after the freshly-extruded molten filamentary streams emerge from the spinneret, they are "quenched" by a flow of cooling gas to accelerate their hardening, so they can be wound to form a package of continuous filament yarn or otherwise processed, e.g., collected as a bundle of parallel continuous filaments for processing, e.g., as a continuous filamentary tow, for conversion, e.g., into staple or other processing.
In the 1980's, Vassilatos and Sze made significant improvements in the high-speed spinning of polymeric filaments and disclosed these and the resulting improved filaments in U.S. Pat. Nos. 4,687,610 (Vassilatos), 4,691,003, 5,034,182 (Sze and Vassilatos) and 5,141,700 (Sze). These Patents disclose gas management techniques, whereby gas surrounded the freshly-extruded filaments to control their temperature and attenuation profiles. These techniques produced yarns with numbers of filaments in the range of 5 to 17, with the latter Patent (the '700 Patent) disclosing nylon yarns. While lower filament count yarns are generally cheaper to make, polyethylene terephthalate yarns of higher filament count are more suitable for commercial fabrics. However, as the filament count of a continuous yarn increases, processability becomes an issue. Moreover, while the '003 Patent in particular is directed to the production of uniform polymeric filaments, there is no disclosure in this Patent or in the other of these Patents ('610, '182 and '700) of denier spread or its effect on uniformity.
Japanese Kokai Patent Application No. Hei 2[1990]-216213 discloses a polyester multi-filament yarn of high uniformity. Although fiber size irregularity is disclosed in this application, there is no disclosure of denier spread in this Application. In addition, no elongation to break is generally disclosed. However, at the spinning speeds and quenching conditions in the Examples given, the resultants yarns would have an elongation to break of less than 100%. Higher values for elongation can be desirable for downstream drawing processes, for example, for draw false twist texturing.
Japanese Kokai Patent Application No. Hei 3[1991]-180508 discloses spinning high strength, low elongation industrial yarns. Again, there is no disclosure of denier spread or of filament count in this Application.
Thus, the prior art fails to disclose a poly(ethylene) terephthalate continuous filament, low denier spread yarn of high elongation with a filament count in a range suitable for economic yet practical processing.